1. Field of the Invention:
This invention relates in general to electric welding systems and in particular to electric welding systems having alternators with remotely controllable outputs. Still more particularly the present invention relates to alternators for use in welding systems which incorporate dual three-phase windings.
2. Description of the Prior Art:
Electric welding units are well known in the prior art. Such units typically include a prime mover, usually an internal combustion engine, which is mechanically coupled to an alternator or generator utilized to generate the voltages necessary for welding.
Several different electric welding techniques are known. For example, so-called "stick" welding utilizes welding rods which are consumed by the electric arc generated between the rod tip and the workpiece. In contrast, heliarc TIG welding or "Tungsten Inert Gas" welding utilizes a high frequency AC voltage and non-consumable tungsten tips for welding aluminum or other similar metals. Finally, MIG welding or "Metallic Inert Gas" welding generally utilizes a consumable welding wire which is generally copper-coated steel. The wire is preferably supplied on a reel and is fed out through a welding unit by a wire feeder.
Conventional stick welders or MIG welders generally utilize four pole, sixteen slot alternators and provide a 60-120 cycle per second pulsated DC output while TIG welding units require a relatively high frequency AC signal source. Thus, it is not possible to utilize a single welder system to do both TIG and MIG welding. Also, it is necessary with known welding units to switch off the unit at the prime mover or main control panel to remove the voltage present at the rod or welding tip. This results in the possibility of accidents occurring while the operator is attempting to turn the unit off.
Many different alternator designs are known and may be utilized to generate the electrical current necessary to perform welding functions. Of the multiple phase alternator designs the delta and wye designs are the most commonly utilized. A wye winding will provide excellent low-speed generation while a delta winding produces better results at high speed. Recently, Motorola Corporation has developed a dual winding alternator which incorporates both a wye and a delta winding in an effort to blend both characteristics; however, this alternator design does not provide the high peak voltages necessary to perform electric welding.
It should therefore be apparent that a need exists for an electric welding system which can perform both MIG and TIG welding and which produces high peak voltages under various loading conditions.